In Patent Application Ser. No. 930264 (EPA No. 1876) filed on even date herewith by E. Vincent Patrick et al for a "Method and Apparatus to Fabricate Image Intensifier Tubes," there is disclosed a unique vacuum chamber system. This system employs a special transport mechanism described in Patent Application Ser. No. 930437 (EPA No. 1877) also filed on even date herewith by E. Vincent Patrick et al for a "Vacuum Sealed Manipulator." The chambers in the vacuum system are generally cylindrical in shape and the manipulator in each chamber is generally a cantilever arm which moves tube parts around a large circle of process stations within the chamber. While the rotation of the arm about the axis of the chamber can be unrestricted, radial movement is limited to 25 mm and axial (vertical) movement to 40 mm. One function of the arm is to move parts into and out of a vacuum lock. With conventional designs, this is very difficult and in general requires extensive additional vacuum hardware and motion feedthroughs.
The conventional interlock uses an external vestibule which is added to a larger vacuum chamber by bolting onto the flange of an access port. The interlock chamber including the part entering or leaving the chamber remains outside the chamber. In the system described above, the manipulator cannot reach outside the chamber to position these parts as required. Additional mechanical devices must be added to the chamber. For example, part cradles that are magnetically propelled through glass walled tubing have been used for this function, but these complicate the task of keeping the chamber clean and can function improperly, on occasion damaging parts or delaying the vacuum processing underway, and by their configuration add a volume that is difficult to evacuate.